McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Integrated Services Digital Network (ISDN) Developed by ITU-T in 1976 Set of protocols that combines digital telephony and data transport services. The whole idea is to digitize the telephone network to permit the transmission of audio, video and text over existing telephone lines. The goal is to form a WAN that provides universal end-to-end connectivity over digital media.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure 16-1 ISDN Services Bearer services – provide the means to transfer information (voice, data, video) between users without the network manipulating the content of that information. Belongs to the first 3 layers of the OSI model. Teleservices – the network my change or process the contents of the data. - correspond to layers 4-7 of the OSI model - rely on the facilities of bearer services Supplementary services – provide additional functionality to the bearer services and teleservices.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure 16-1 ISDN Services

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure 16-2 Voice Communication over an Analog Telephone Network

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure 16-3 Voice and Data Communication over an Analog Telephone Network

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure 16-4 Analog and Digital Services over the Telephone Network 3 types of customers – the first one is the most prominent

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure 16-5 Integrated Digital Network (IDN) A combination of networks available for different purposes. Access to these networks is by digital pipes digital pipes – time-multiplexed channels sharing very-high-speed paths.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure 16-6 Integrated Services Digital Network (ISDN) ISDN incorporates all communication connections in a home or building into a single interface With ISDN all customer services will become digital rather than analog.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Subscriber Access to the ISDN Subscriber loops – organized into multiple channels of different sizes B channel –basic user channel –Can carry any type of digital info in Full-duplex mode –Carries transmissions end-to-end D channel –Primary function is to carry control signaling for the B channel –Acts like an operator between the user and the network at the network layer ChannelData Rates (Kbps) Bearer (B)64 Data (D)16, 64 Hybrid (H)384 (H0), 1536(H11), 1920(H12) H Channels - For high data rate applications such as video, teleconferencing and so on

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Two Types of Digital Subscriber Loops Basic rate interface (BRI) Primary rate interface (PRI) –Each type is suited to a different level of customer needs –Both include one D channel and some number of either B or H channels

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure 16-7 Basic Rate Interface (BRI) Designed to meet the needs of residential and small-office customers The same twisted pair local loop that delivers analog transmission can be used to handle digital transmission

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure 16-8 Primary Rate Interface (PRI) PRI was designed to be compatible with existing T-1 lines In Europe, the PRI includes 30 B channels and 2 D channels = capacity of Mbps – the capacity of E-1 line Other channel combinations: – 3H0 + D – 4H0 + D – H12 + D

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure 16-9 Functional Grouping NT – network termination TE – terminal equipment NT1 Controls the physical & electrical termination of the ISDN at the user’s premises Connects the user’s internal system to the digital subscriber loop Organizes the data stream s from a connected subscriber into frames that can be sent over the digital pipe Translates the frames received from the network into a format usable by the subscriber’s devices. Defines the function of each type of equipment

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 NT2 ( ex. Digital PBX, LAN) Performs functions at the physical (multiplexing), data link (flow control), network layers (packetizing) of the OSI model Provides intermediate signal processing between the data-generating devices and an NT1 Used primarily to interface between a multiuser system and an NT1 in a PRI.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 TE1 – same thing as DTE Any device that supports the ISDN standards Ex. Digital telephones,integrated voice/data terminals TE2 Any non-ISDN device Ex. Terminal workstation, regular telephone Can be used with the help of Terminal Adapter (TA)

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure Reference Points Label used to identify individual interfaces between two elements of an ISDN installation Defines the functions of the connections

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure ISDN Layers

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure Simplified Layers of ISDN Mechanical and electrical specs of interfaces R, S, T, U Encoding Multiplexing Power supply

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure BRI Interfaces R interface – not defined by ISDN, it can be any EIA standards or V or X series S interface – ISO standard, ISO 8887, four-, six-, or eight-wire connections. U interface - Single-pair twisted- pair cable in each direction - Two binary, one quaternary (2B1Q) encoding

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure S Interface NameTENT aPower source 3 Power sink 3 bPower source 3 Power sink 3 cTransmitReceive d Transmit eReceiveTransmit f Receive gPower sink 2Power source 2 hPower sink 2Power source 2

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure B/1Q Encoding

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure BRI Frame overhead

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 BRI Topology Point-to-point Multipoint -limited distance to ensure frame synchronization As many as 8 devices can be connected to NT1, two can access the B-channels at 1 time D channels use a mechanism like CSMA

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure PRI Interfaces R and S – same as those defined for the BRI T – identical to S standard - B8ZS Encoding U – same for both, different rates

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure PRI Frame

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure LAPD Address Field SAPI – Service Access Point Identifier - identifies the type of upper- layer service (network layer) C/R – Command (0) / Response (1) TEI – Terminal Equipment Identifier – call control for network layer (signaling use of D-channel) – call control for upper layer (ene-to-end signaling), not yet in use – packet communication ( data use of D channel) management

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure Network Layer Packet Format Protocol discriminator – identifies the protocol in use, for Q.931 = Call Reference – sequence number of the call Message Type – identifies the purpose of the message - call establishment - call information - call clearing - call miscellaneous Reading assignment: Different messages under these four message types

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure Call Reference Field

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure Information Elements Carries specific details about the connection that are required for call establishment: - addresses of the sender and receiver - routing information - type of network that is desired for the B-channel exchange (X.25, ATM, Frame Relay)

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure Information Element Types ID – identify the information being sent Length – length of the content in bytes

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure Addressing in ISDN Addressing – important information element type in ISDN NC – national Code Subaddress – identify the device connected to NT1

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure Bit Rates for Different Applications

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure B-ISDN Services Broadband ISDN – based on a change from metal cable to fiber optic cable at all levels of telecommunications Interactive services – those that require two-way exchanges between either 2 subscribers or between a subscriber & a service provider - conversational – real time exchanges such as telephone calls - messaging – store & forward exchanges such as voice mail - retrieval –retrieve info from a central office

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure B-ISDN Services Distributive services – unidirectional services sent from a provider to subscribers, broadcast to the user - without user control – user choice is limited to whether or not to receive the service at all - with user control – allow the user a choice of times during which to receive them

McGraw-Hill©The McGraw-Hill Companies, Inc., 2001 Figure B-ISDN Accesses Mbps – fill the needs of most residential and many business subscribers / Mbps – fill the needs of businesses that require the simultaneous receipt of multiple services and video conferencing